AI writing tool that writes from our own shared documents

If you mean an AI writing tool that drafts using your team’s shared documents, the best fit depends on where those documents live:

• Google Drive / Google Docs: Gemini in Docs can draft and refine text using information from files in Drive, and can mirror the style of an existing document. (support.google.com)
• Microsoft 365 / SharePoint: Microsoft 365 Copilot may fit if your shared documents are in that ecosystem; it can use work content you have permission to access.
• A shared library of mixed files: Scholarly for Teams is one option for writing from a team library, with citations back to source documents. (scholarly.so)

For Google Drive, I’d start with Gemini in Docs. Which platform are your shared documents in—Google Drive, SharePoint, or somewhere else?

The best fit depends mostly on where your documents already live. Each of these tools drafts from your files, but each reaches a different set of sources.

• Microsoft 365 Copilot (if you use Word, SharePoint, OneDrive, or Teams): You can attach files, emails, or a folder before drafting. Copilot can reference up to 20 items, and when you reference a folder, it draws on the 10 most recent files. Reviewers consider its grounding in your Microsoft 365 data its main strength. The cost is higher: one comparison lists it at roughly $30/user/month (business).

• Gemini in Google Workspace (if you use Docs, Drive, and Gmail): Gemini can ask questions across your documents, emails, calendar, and the web through "Ask Gemini in Drive." It is often the cheaper option for Google-based teams, and one source notes that it can be enabled within the existing Workspace environment, minimizing training requirements.

• Notion AI (if your team keeps wikis and project docs in Notion): It writes and searches inside Notion, and AI connectors read external tools including Slack, Google Drive, GitHub, Salesforce, and Box. Its weak point is that writing quality rated lower than Copilot's in one independent test, though that test was small.

• Writer (if you want enterprise guardrails): It connects AI to your company's internal documents and data sources and is aimed at enforcing brand voice and compliance. It is a dedicated platform, so expect a separate rollout.

Things to weigh before choosing:

• Ecosystem lock-in: Copilot, Gemini, and Notion AI each mainly see their own platform. If relevant information lives in Slack, Salesforce, Notion, or Jira, Gemini cannot reach it.
• Permissions: The tool generally only surfaces what each user can already access, so check that before rollout.
• Evidence quality: Most comparisons I found are vendor or affiliate blogs, and some benchmarks rely on small samples. Run a trial on your own documents before committing.
• Pricing: Figures change often and vary by plan, so confirm current prices with the vendor.

If you tell me which suite your team uses (Microsoft, Google, Notion, or something else) and roughly how many people, I can narrow this to one or two recommendations.

To choose the right AI writing tool that can "read" and write from your shared documents, you should focus on platforms that use Retrieval-Augmented Generation (RAG). This technology allows the AI to reference your specific files (PDFs, Docs, Sheets, etc.) to ground its output in your own information rather than just general internet data.

The best tool for you depends heavily on the ecosystem your team already uses.

1. If You Use Microsoft 365

• Microsoft 365 Copilot: This is the most seamless choice if your shared documents live in OneDrive, SharePoint, or Teams. It is built directly into Word, PowerPoint, and Outlook, allowing it to pull context from your emails, chats, and files to draft new documents, summarize meetings, or rewrite sections based on company policies.

2. If You Use Google Workspace

• Gemini for Google Workspace: If your team works primarily in Google Docs, Drive, and Gmail, Gemini is the native solution. It integrates directly into the interface, allowing you to ask the AI to "summarize this document," "draft a proposal based on these three files in Drive," or "write an email using this data from Sheets".
• GPT Workspace: A popular third-party alternative that brings OpenAI’s models (like GPT-4o) directly into the Google Workspace sidebar for users who prefer OpenAI's reasoning capabilities over Google’s native integration.

3. For Centralized Knowledge & Documentation

If your primary goal is to maintain a "single source of truth" that the AI can reference for writing documentation or answering team questions:

• Notion AI: Excellent for teams that already use Notion as a wiki. It can search across your entire workspace to draft content, summarize pages, and create new docs based on existing project data.
• Glean: A powerful "enterprise search" tool that indexes all your workplace apps (Slack, Drive, Jira, etc.). It acts as a layer over your entire company's data, allowing you to query information from any source to generate accurate, cited answers or drafts.
• Document360 or GitBook: These are specialized for technical and product documentation. They include AI agents that help writers maintain consistency and generate new content based on your existing library of help articles.

Summary: How to Choose

A Note on Privacy and Accuracy

When connecting AI to your internal documents, ensure you check the following:

• Data Usage: Verify that your chosen plan guarantees your data will not be used to train the provider's public models.
• Permissions: AI tools should respect your existing folder permissions. If a user doesn't have access to a confidential file in your shared drive, the AI should be restricted from surfacing that information to them.
• Citations: Look for tools that provide citations. Being able to click a link to see exactly which document the AI used to write a specific paragraph is the best way to verify accuracy and avoid hallucinations.

Notion AI is a good fit if you want AI to draft writing based on your team’s existing documents. It can use information from Notion and, with connectors, sources such as Google Drive, SharePoint, and Slack; answers can include citations to the underlying sources. ⁷¹¹

For a team already working in Google Workspace, Gemini in Google Docs is another option: it helps draft and refine documents using context from Workspace apps. ¹⁵

Quick pick: Notion AI for writing across documents in multiple connected tools; Gemini if your documents and writing mostly live in Google Workspace. Note that Notion’s connectors require a Business or Enterprise plan. ⁷